Kingdoms and Domains Sec 1.3

Crash Course!  47-g6tlA 47-g6tlA

Structural diversity  All species on Earth shared certain fundamental similarities such as being made up of cells and having DNA.  However, if biologists were to study the structural diversity (the diversity based on the external and internal structural forms in living things) of all living things, it would be too immense a topic.  Therefore, biologists study the similarities and differences at a higher taxonomic rank such as kingdoms and domains.

Kingdoms over time  1800’s – Kingdoms were the highest rank of classification and plants and animals were the only taxons.  1860’s – Single-celled organisms were added through the Kingdom Protista.  1930’s – Single-celled organisms without a nucleus were classified under the Kingdom Bacteria.  1960’s – Fungi were so different they eared their own kingdoms.  1990’s – New genetic information led to the splitting of the Bacteria Kingdom into Bacteria and Archaea.

Two Major Cell Types  There are two main cell types that are significant for the kingdom classification.  Prokaryotic cells – a smaller simple type of cell that does not have a membrane-bound nucleus.  Prokaryotic – before the nucleus  Eukaryotic cells – a larger and complex type of cell that does have a membrane-bound nucleus.  Eukaryotic = true nucleus

Domains  As scientists continued analyzing organisms in the kingdoms, the differences between the two groups at the genetic and cellular levels were so great that each group was elevated to a new rank, higher than kingdom – domain.  As a result of reclassifying these kingdoms as domains, the remaining 4 kingdoms were reclassified into a domain of their own – Eukarya (because all organisms have eukaryotic cells).

Main characteristics  Distinctions can be made between the kingdoms based on several characteristics:  Cell type  Cell wall – absent in animals but the composition varies in other organisms.  Nutrition  Autotroph – an organism that obtains energy by making its own food.  Heterotroph – consumes other organisms to obtain energy – yielding food.  Reproduction – asexual reproduction can be found in all kingdoms, however sexual reproduction can be found in al kingdoms, however sexual reproduction is a trait that only occurs in Eukarya.

DomainBacteriaArchaeaEukarya KingdomBacteriaArchaeaProtistaPlantaeFungiAnimalia Cell TypeProkaryote Eukaryote # of cellsUnicellular BothMulti - cellular Mostly Multi - cellular Multi - cellular Cell wall material peptidogly can Not peptidogly can or no cell wall Cellulose or no cell wall CelluloseChitinNo cell wall NutritionA and H AHH Reproductio n (Primary) Asexual Asexual and Sexual Sexual

And now….Viruses!

Viruses  A Structure that contains strands of DNA or RNA surrounded by a protective protein called capsid.  There is a debate in the scientific world about whether viruses are living or non living

Viruses – Evidence for non- living  Functionally dependent on the internal working of cells (prokaryotic or eukaryotic).  Cannot live independently outside of cells (they are dominant).  Must invade cells and use the host cell’s machinery for survival and reproduction.  Are not cellular – have no cytoplasm, membrane-bound organelles or cell membranes.

Viruses – Evidence for Living  Have genetic material.  Reproduce.  Affect the lives of other organisms.  Cause diseases in plants and animals which can affect population, species, and ecosystems.  Uncontrolled infection can lead to food shortages around the world.  Other viruses affect humans lead to severe illness (polio, HIV, H1N1)  Used in biotechnology to clone copies of genes.

Classifying Viruses  Since viruses can’t unanimously be determined as living organisms, they are not classified using the Linnaeus system.  Viruses are classified by the size and shape of their capsid.  Viruses are also grouped by the types of diseases they cause.